Servicing couplings of the aforedescribed kind are generally employed to permit the charging and evacuation of the refrigeration circuit of refrigeration systems. For this purpose the charging port part and the service adapter are connected to each other, whereupon the self-sealing valve of the charging port part is opened. The flow of refrigerant through the service adapter is generally controlled by a manually operated adapter valve.
A fundamental problem with such known service couplings exists, however, in the axially adjustable adapter valve, which is under great breech-closing spring pressure since, as a result of the rotation of the valve stem acting as spindle for the axial displacement of the valve body relative to the valve seat, great tangential force is present between the valve body and the valve seat, which force quickly destroys the valve seal, so that the service adapter becomes leaky to a critical degree after little use.